Thulis said:
Do they give any explanation for how Ork PCs don't contaminate every world they visit with their and their pets' spores?
Not really. As I recall, it suggests that the spores take a long time (sometimes centuries) to grow, and it also intimates (or gave me the impression) that it required a fairly large number of Orkoids to produce a significant risk of them growing at all.
Still, I think it is designe as one of the drawbacks of the RT having an Ork on board. On ship (or other non-fertile location) the spores have a much more difficult time growing, and the frequent use of flamers to scour the living area is also suggested/recommended. On a planet, however, it is a bit more difficult. Personally, I think that keeping the Ork in his void suit, or other mostly-sealed suit of armor/clothing, should serve fairly effectively to minimize/negate the risk on-planet.

